In order to better describe the invention, the evolution of this type of wheel will be described.
A conventional wheel comprises a hub, a tire, and a wheel body, for example, spokes. In a first stage of development, the tire was flexible, then it was made pneumatic. The tire was then developed to replace the wheel body in entirety. This is the final stage of evolution corresponding to a complete elimination of the wheel body and is known as a pneumatic wheel. Such wheel is described in U.S. Pat. No. 2,190,905.
The direction of this evolution which at the beginning sought comfort has evolved towards an adaptation to soft ground through the concern and the possibility of obtaining small light wheels which would not sink in the ground. The invention corresponds to a continuation of this evolution in the same direction to obtain even smaller, lighter wheels which will not sink in soft ground.
The pursued objective is therefore clear: with respect to the method, it consists of seeking to develop the advantageous possibility of deformation of the inflatable tire so that the surface of contact with the ground will be as great as possible. Fig. 1 of U.S. Pat. No. 2,190,905 clearly shows the capability of much greater deformation than conventional tires. By analyzing the deficiencies of recent pneumatic wheels, it will be shown how one can still advance even further.
In fact, wheels of average size best adapted to soft ground are, at present and without doubt, pneumatic wheels. For easy travel on such ground these wheels inclusive of the wheels of the aforenoted U.S. patent have two deficiencies:
1. They are too large. In fact, they are never less than a diameter of 30 - 40 cm. undoubtedly, they would be much more expensive if made smaller, but there is also another reason which is less evident: on soft ground in order for a wheel not to sink, it should be especially soft as it becomes small. When a small wheel is made with the same material of a satisfactory large wheel, it therefore would become overloaded, or too thin or too hard. By definition, in order to make the wheels smaller yet with the same properties, it is necessary to adapt a more flexible material.
2. THE HUB IS CONNECTED TO THE TIRE. This is certainly not a deficiency in and of itself, and this corresponds, in contrast, to the possibility of driving the wheel through its hub; however, from an examination of FIG. 1 of the aforesaid U.S. Patent, it clearly appears that by elimination of this capability, one could eliminate all reinforcement of the polar regions and even all connection between the hub and the tire, which would immediately lead to a much simpler manufacture and much greater deformation. Experience shows that these possibilities of deformation are real, however, on the condition that the material of the tire is itself made more deformable and more flexible than the materials in actual use. By realizing a pneumatic wheel whose tire is sufficiently flexible with a hub to which it is not connected, the two deficiencies are overcome. This is the aim to be attained by the present invention whose object is to provide a pneumatic wheel constituted by an inflatable element of substantially toroidal shape with a tubular central passageway and a hub disposed in said central passageway, said pneumatic wheel being characterized by the elimination of any connection between the hub and inflatable element, such that the latter can freely deform in the vicinity of the hub.
The two principal characteristics of the invention reside in the use of a more flexible tire and in the absence of any physical connection between the tire and the hub. Moreover, the invention is not concerned with the tire alone, as satisfactory tires already exist. Furthermore, the manufacture of such inflatable tires with a central tubular passage from a plastisol is known from French Pat. No. 1,423,095 (Verigold). The tires are produced therein by rotation and they have sufficient flexibility.
It is in the independence of the tire and the hub that the essential characteristics of the invention reside because this permits on the one hand the selection of the tire from those currently existing and on the other hand a substantial doubling of the practical performance of the wheel.
The wheels according to the invention provide three categories of advantages:
1. Simpler and therefore more economical manufacture.
2. Better performance, because for equal sizes, they can carry as much with a fraction of the pressure.
3. The capability of making the wheels considerably smaller, up to 10 cm. in diameter, without any sinking whatever.
By simply using tires made by rotation (method cited above) one can select from an available range of sizes, shapes, thicknesses and of suitable materials in order to be able to equip small handling appliances currently existing or for development in the future, (toys, carts, baby carriages, wheel barrows, etc.) with wheels exactly adapted to each appliance and to the ground on which it is to travel. For very light wheels as well as wheels especially adapted for travel on dry beach sand, and sand hills and able to easily roll under a weight reaching and even exceeding fifty times its weight (100 kg. for a wheel of 2.5 kg., 15 kg. for a wheel of 250 g.). Carts equipped with wheels of this type make transport easy, even for children, of heavy loads such as bottles of liquefied gas, jerrycans, garbage cans, etc. over plowed earth, sand, gravel and even steps.
According to a particular embodiment of the invention, the hub comprises a tube engaged in the central passage of the inflatable element, and the tube is closed at its ends by closure elements which expand the ends sufficiently to prevent the tube from separating from the central passage.
Elongated and endowed with two bearings, the hub is excellent. Furthermore, since it only has to resist insignificant forces, it can be flexible which is not a property to be ignored.
These great possibilities of deformation, accompanied with the simplicity provided by the wheel of the invention, provide a vast field of use. These wheels, which do not sink, can be made resistant to rusting by making the bearings of plastic and the axle of stainless steel. They are then perfectly adaptable for handling on beaches (transport from ships, etc.).
According to another embodiment of the invention, the hub comprises in the vicinity of its ends, two external annular collars opposing transverse sliding of the wheel while reinforcing the terminal portions of the hub.
The closure members form bearings and are prevented from separating from the hub due to the formation of annular elastic lips at the extremities of the hub which enclose the rear of the closure members after the latter have been forceably introduced into the hub. For convenience in mounting, the closure members are substantially frusto-conical and flared to a maximum diameter substantially greater than the internal diameter of the hub, so as to progressively dilate the extremities of the hub during their introduction. They include at the rear a portion of reverse conicity on which the lips of the hub come to rest thereby confining the closure members in the hub.
According to an advantageous characteristic of the invention, the hub has internal shoulders formed in its inner surface serving to limit the degree of penetration of the closure members. These shoulders can be constituted by the edges of an annular step formed by increased thickness of the wall in the central portion of the hub. In addition to its role as an abutment, such step in thickness confers to the hub a greater rigidity in its central portion.
In a modified arrangement, one of the bearings for the axle is directly incorporated by moulding into the hub. In this regard, the wall of the hub is thickened in the vicinity of one of its extremities and presents a cylindrical bore for the passage of the axle. The other extremity of the hub has a uniform thickness, sufficiently small, to be able to be deformed and introduced into the central passageway of the tire.